ULTRASTRUCTURE OF SPERMIOGENESIS AND THE SPERMATOZOON OF APORINA-DELAFONDI (CYCLOPHYLLIDEA, ANOPLOCEPHALIDAE), INTESTINAL PARASITE OF TURTLE DOVES IN SENEGAL

Spermiogenesis in Aporina delafondi begins with the formation of a dif ferentiation zone bordered by cortical microtubules and containing fro m the beginning a portion of nucleus and two parallel centrioles. One of the centrioles aborts, the other gives rise to a flagellum. The cor tical microtubules elongate and spiralize while the nucleus migrates a long the axoneme and crest-like bodies form at the level of the differ entiation zone. The old spermatid separates from the residual cytoplas m by strangulation of the ring of arched membranes. The mature spermat ozoon lacks mitochondria, is filiform and tapered at both its extremit ies. Its anterior extremity is capped by an apical cone of electron-de nse material and exhibits five crest-like bodies of unequal lengths on its periphery. Its cortical microtubules are regularly spiralized exc ept at their posterior extremity where they become parallel to the spe rmatozoon axis. The cytoplasm is slightly dense in the anterior region s (I and II) and exhibits many protein granules and patches of electro n-lucent material in the middle (III) and posterior zones (IV and V). The nucleus is an electron-dense cord coiled in a spiral around the mi ddle region (III) of the axoneme. This is of the 9 + ''1'' pattern and ends before the posterior extremity of the gamete. Spermiogenesis in Aporina delafondi differs from that of the other Cyclophyllidea by the very early movement of the nucleus into the differentiation zone, the formation of a ring of arched membranes in the distal part of the dif ferentiation zone, the appearance of crest-like bodies during migratio n of the nucleus and the formation of a cytoplasmic bud which contains the abortive centriole and develops to temporarily form a large later al extension. The mature spermatozoon differs from that of the other C yclophyllidea in the presence of lucent patches in its cytoplasm and o f five helicoidal crest-like bodies. The systematic position of the ge nus Aporina is also debated.